#include <math.h>
#include <iostream>
using std::cout;
using std::endl;

/* class Point2; */
/* class Point2{}; */

class Point;//前向声明

class Line{
public:
    float distance(const Point & lhs,const Point & rhs);

    void setPoint(Point & pt,int x,int y);
};

class Point{
public:
    Point(int x,int y)
        : _ix(x)
          , _iy(y)
    { cout << "point(int,int)" << endl; }

    //友元声明
    friend Line;
    /* friend class Line; */
private:
    int _ix;
    int _iy;
};


float Line::distance(const Point & lhs,const Point & rhs){
    return sqrt(pow(lhs._ix - rhs._ix,2)+ 
                pow(lhs._iy - rhs._iy,2));
}

void Line::setPoint(Point & pt,int x,int y){
    pt._ix = x;
    pt._iy = y;
}

void test0(){
    Point pt(0,0);
    Point pt2(3,4);
    Line ll;
    cout << ll.distance(pt,pt2) << endl;
    ll.setPoint(pt2,12,5);
    cout << ll.distance(pt,pt2) << endl;

    /* Point2 pt; */
}

int main(void){
    test0();
    return 0;
}
